HP 3000 Manuals

Silhouette Reference Manual

System Components 

The Silhouette system consists of four components:

 *  The Manager Program (MP)

 *  The Communication Process (CP)

 *  The Recovery Process (RP)

 *  The Tape Process (TP)

Throughout this manual these processes are referred to and used to
explain how Silhouette functions.  The following sections provide a brief
explanation of each of these processes.

Manager Program (MP) 

The Silhouette Manager Program (MP) is the user interface for Silhouette.
It is used to control the other processes and provides status information
to the user.

The MP is invoked when you enter RUN SILMP.PUB.SYS to access the system.
Thereafter it only needs to be present while the system is being started.
It may be terminated any time after the >START command completes, leaving
the Silhouette jobs to carry on the database duplicating functions.

The MP normally runs in a session, while all other components of
Silhouette run in batch mode.  Any command may be passed to the MP via
the INFO = parameter of the MPE :RUN command.  This allows the use of
UDCs when performing functions such as starting or stopping the system,
or requesting a STATUS report.

Communication Process (CP) 

The Communication Process (CP) exists on both the primary system and the
secondary system.  On the secondary system the CP is referred to as the
Secondary Communication Process (SP).

On the primary system the CP creates a Tape Process (TP) which is
activated if the high water mark is exceeded.  It also performs
initialization processing such as opening the communications line,
creating the SP on the secondary system, or transmitting data to the SP
on the secondary system via the communications line.

On the secondary system the SP creates the Recovery Process (RP) if one
does not already exist, accepts data from the CP on the primary system,
and sends the data to the RP via message files.

Recovery Process(RP) 

The Recovery Process (RP) exists only on the secondary system.  It
accepts data from the Secondary Communication Process (SP) and updates
the database, SAVE file, and logfile.  The RP also maintains some control
information such as the record number of the last successfully
transmitted logfile record, and the status of any incomplete transactions
or super transactions.  The RP also accepts and executes commands issued
from the Manager Program (MP) on the secondary system.

Tape Process (TP) 

The Tape Process (TP) is created by the Communication Process (CP) on the
primary system only.  The TP is activated if the backlog of logfile
records not sent to the secondary system exceeds the MAXREC = value
specified in the configuration file.  This value is known as the high
water mark.  The TP opens a tape file and writes the records not sent to
the secondary system to tape.  This occurs if the secondary system or a
communications line fails.  The data on the tape can be used for recovery
purposes in the event of a primary system failure.

MPE/iX 5.0 Documentation